Constraining the anisotropy structure of the crust by joint inversion of seismic reflection travel times and wave polarizations |
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| Authors: | Jingyi Chen Jiwen Teng José Badal |
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| Institution: | (1) State Key Laboratory of Lithosphere Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China;(2) Physics of the Earth, Sciences B, University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain |
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| Abstract: | In the context of wide-angle seismic profiling, the determination of the physical properties of the Earth crust, such as the
elastic layer depth and seismic velocity, is often performed by inversion of P- and/or S-phases propagation data supplying
the geometry of the medium (reflector depths) or any other structural parameter (P- or S-wave velocity, density...). Moreover,
the inversion for velocity structure and interfaces is commonly performed using only seismic reflection travel times and/or
crustal phase amplitudes in isotropic media. But it is very important to utilize more available information to constrain the
non-uniqueness of the solution. In this paper, we present a simultaneous inversion method of seismic reflection travel times
and polarizations data of transient elastic waves in stratified media to reconstruct not only layer depth and vertical P-wave
velocity but also the anisotropy feature of the crust based on the estimation of the Thomsen’s parameters. We carry out
a checking with synthetic data, comparing the inversion results obtained by anisotropic travel-time inversion to the results
derived by joint inversion of seismic reflection travel times and polarizations data. The comparison proves that the first
procedure leads to biased anisotropic models, while the second one fits nearly the real model. This makes the joint inversion
method feasible. Finally, we investigate the geometry, P-wave velocity structure and anisotropy of the crust beneath Southeastern
China by applying the proposed inversion method to previously acquired wide-angle seismic data. In this case, the anisotropy
signature provides clear evidence that the Jiangshan-Shaoxing fault is the natural boundary between the Yangtze and Cathaysia
blocks. |
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| Keywords: | P-wave travel times Polarization angles Joint inversion Crustal anisotropy Southeastern China |
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